Process of drying paper



Feb 9 E. A. BRINER ET AL f PROCESS OF' DRYING PAPER Filed NOV.A 29, 1919 2 Sheets-Sheet l |00 75 CONTAINED MOISTURE AS A PERCENTAGE OF WEIGHT OF DRY FIBRE,AT TIF'IEDRYING M5 CHANGED FROM CONSTR/UNED T0 FREE.

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E. A. BRINER ET Al.

PROCESS OF DRYING PAPER Filed NOV. 29, 1919 2 Sheets-Sheet E I HENRY J. GUILD, citizens of the United` Patented Feb. 16, 1926.

UNITED STATES PATENT OFFICE.

EMIL A. BRINER, vOIE EAS'l.` ORANGE, NEW JERSEY, AND HENRY J. GUILD, OF BANGOR, MAINE; SAID GUILD ASSIGNOR TO EASTERN MANUFACTURING COMPANY, 0E BOSTON, MASSACHUSETTSfA CORPORATION 0F MASSACHUSETTS.

PROCESS OF DRYING PAPER.

Application filed November 29, 1919. Serial N0. 341,359.

To all whom t may concern.'

Be it known that we, EMIL A. BRINER and States, respectively residing at East Orange, in the county of Essex and State of New Jersey, and at Bangor, in the county of Penobscot and State of Maine, have invented new and useful Improvements ain Processes of Drying Paper, of which the following is a specification.

For the intelligent understanding of this yprocess and the apparatus adapted to carrying it out it is necessary to clearly comprehend certain general laws having to do with the drying of paper and similar materials,

which laws we have ascertained by careful quantitative experiments undertaken in connection with the working out of this invention. These laws, particularly in their bearing upon the invention, will first be eX- plained, and afterwards we shall point' outtheir application to the securing ofoptimum results in the drying of paper.

The formation of a sheet ofpaper proceeds from the initial entanglement of the papermaking fibers in partial water suspension as the wet stock is flowed on the wire, through the progressive establishment of intimate contact between these fibers as the water is ,removed by natural drainage, vby suction and by pressure; and finally to the drying of this web of interlaced or felted fibers into a sheet, the tenacity'of which depends upon the character and relative position of the fibers and their hold upon each other, and the smoothness of which depends upon the evennessl with which the initially fiat wet sheet dries into a flat dry sheet` The selection of stock, beating, refining, and sheet-formation,--things with which our invention is not directly concerned,-fiX the characterof the wet sheet and hence determine the best results-as to strength and flatness among other thingsthat may finally be obtained if none of the possibilities are lost in drying.

The drying operation in existing paper- -machines has valways heretofore been, carried out under well established conditions. In order to insure'fiatness of the sheet, the initially wet web of paper traveling from the press-rolls is held firmly in contact with the successive hot drying rolls lor cylinders under relatively strong tension where it passes from one drying roll to another. This paper is mechanically held under restraint from shrinkage and is not allowed to take up its own dimensions during this drying process; and it will be shown that this has an important effect on strength, and that great improvement may be realized by departure in certain matters from thisstandard practice.

Top-sized papers, coated papers, and

4other special papers are more or less superficially wetted again by their respective subsequent treatments afterlthe completion of the principal drying operation just noted, and certain methods other than those indicated have been used or disclosed for the second drying of such papers; but these methods are concerned with what'is essentially an after-treatment, and are applied at a time subsequent to the end of the phase that we have found to be by far the most responsive or susceptible in the matter of effect of drying methods on strength--as will be explained.

Our experiments developed some facts of importance that were hitherto unknown, and checked or modified some conclusions which had been regarded as established or generally accepted.

It was first found that paper dried in the customary manner just described, where the web is under strong constraint throughout 'the' drying,Ir process, showed both a bursting and a tensile strength much inferior to that of a specimen of the same paper taken from just beyond the press-rolls and air-dried without resort lto any strongly effective mechanical expedient to maintain fiat-ness. Onl

'"chanical hold upon the wet or damp web,

universally accepted as a necessary evil, in view of the requirement for flatness, and it was the purpose ofj our investigation to. determine precisely how and where the loss occurred, and further to determine whether any process and apparatus could be developed whereby retention of substantially vmaximum strength could be rendered compatible with the production of a flat and acceptable sheet.

rlhe general procedure in this investiga-y tion was as follows: r ,n

During a run of a known grade and weight of paper over a paper-machine of the usual type, a large sample was taken off just after the groups of results similarly compared.,`

and plotted as in Figure l.

' These tests/disclosed the unsuspected and important fact that the loss of 'strength did not occur progressively during the entire process of constrained drying as was anticipated; on the contrary, nearly all of the detrimental action was limited to one rather brief phase of the drying process.

rlhey established the following novel and valuable conclusions; that there is a first critical moisture percentage, remarkably definite for each kind of paper, to which drying under strong lmechanical constraint can be carried without appreciable detriment to strength; but beyond which the continuance of any form of eective strong meand particularly the continuance of the customary amount ofv tension, causes a marked progressive decrease of strength which goes on cumulatively as a result of the usual drying procedure, through what may be termed the responsive or susceptible drying phase or moisture zone, and ceasesd again somewhat abruptly at a second critical point when the paper becomes nearly dry. This' relation is shown by the aforementioned plot marked Figure 1 to which further explanatory reference is made below, ln a certain QS-roll drier with which we worked, the first critical moisture percentage was reached for most writin papers just after the 12th roll.

lVe also oundthat specimens of paper taken very wet after contact with only afew of the first drying cylinders behaved in greater or less degree as did those taken directly after the press-rolls, showing on air-drying a tendency to cockle or dry invase? y with marked irregular local departures from flatness,'.which tendency could not be overcome without resort during the early part of the drying to mechanical constraint as severe as that which would have beenenforced by further passage through the pawithout development of cockle or other ob- -v jectionable departure from flatness.

The eXperiments disclosed the further important 'fact that this fairly definite moisture percentage at which the paper could be taken off from the machine and the drying be successfully contained in the airor otherwise Without marked mechanical enforcement of flat-ness,-was substantially coincident with the previously mentioned 'remarkably definite' first critical point, where the percentage offmoisture marked the begmning of the phase susceptible to injury through drying under the customary stretch and mechanical hold.

rlhese two discoveries taken concurrently showed first that if full strength is to be conserved, the progressively drying paper must be freed pfrom mechanical. restraint when, or before, it has dried down to a definite critical percentage of moisture; and second that, if flat drying is to be accomplished, the paper Vmust not be freedrfrom such restraint until when or after ithad reached substantially this same critical moisture percentage.

The practical identity of the point beyond which drying under strong constraintmay not. go without detriment to strength, and the point to which it must Vgo to insure ab-v sence of cockle, is not thought to be a mere coincidence,-as subsequently explained.

We have found then that, in order to get an optimum flatpaper having unimpairedstrength, the initial period of drying under relatively strong constraint, such as that found on a paper-machine, must proceed to, but not beyond a critical point, definite for that paper; and that thereafter 'drying must proceed with7 the paper free kor sufficiently so, to practically assume its own dimensions, as in air drying, until another definite point near dryness, after which constraint again becomes unobjectionablei During the commercial operation of a drying apparatus embodying this principle, the percentage of moisture content ofthe paper at the point of transfer ,from mechanically controlled to mechanically free drying, will unavoidably wander somewhatl vfrom the exact value sought, any such depar-v ture, ifvappreciable in amount, willlhave some detrimental effect on flatness if infone direction or strength if in the other'. Careful attendance, supplemented if necessary by lone of the well-known devices for controlling the temperature of the drying rolls, will be suiiicient to maintain an adherence to best conditions sufficiently exact to insure great benefit; it will be readily understood, however, that a mere rough approximation to the optimum is not sufficient for best results. Further, the conditions obtaining during air-drying are by no means a matter of indifference, and those found to be best are indicated in due course.

Our theory as to the explanation of the various facts that we have discovered seems to us to further elucidate the matter, and toy render more easy the practice of our invention, and the development of slight modifications within its scope; we therefore outline this theory, although it is to be carefully observed that the benefits and improvements that we have obtained can be fully realized through the exercise of reasonable skill in following the directions herein set forth, without acceptance of, or vregard to, the correctness of our theory.-

lVe conclude that the paper-making fibers, during the initial wet phase of mechanically constrained drying, move or slip upon each other so that they establish progressively new mutual relations as the necessarily uneven drying goes on and as vaporis discharged from the wet mass, and that, so long as a very large percentage of water is present, this water and the hydrolyzed sur- Jface of the fibers act as a lubricant, which, in conjunction with the mechanically loose iiber arrangement of the water-permeated sheet, allow such slippages to be continually occurring and mending themselves without bringing about new fiber relations inferior to the old as al starting point for the progressive establishment of the mechanical and adhesive bond between the fibers when in due course the drying comes toward its -fnal stages'.

On the other hand, when drying has proceeded to a stage where there is no more water mechanically held by capillarity between the fibers, or wetting their surfaces, then we conclude that further drying out ofjthe wa-tersmore intimately absorbed or combined in the fibers "themselves has a different result thatexpla-ins the sudden change lin 'effect of stretch or'constraint. After this point; further relative movement of the libers can indeed take place, and the bond between them is permanently injured thereby` as in an incipient tear. This injury may be'partly analogous to the injury to the adh'esive bond between two glued surfaces which results if movement takes place after a partial setting of the glue; also an incipient mechanical disentangling or de-felting action doubtless occurs, and a full re-establishment of mechanical intertwining is not possible on account of the impaired freedom of motion of the fibers in the damp as compared with the wet sheet. Further, our experiments appear to show that the beginning of the drying out of this water of hydration (as it may be called in contrast to the mechanically held water) marks the beginning of the shrinkage of the paper at a -deiinite rate proportional to the loss of moisture ;*a fact which is believe :l to indicate the establishment of a definite inter-iiber relation at this point, after which undue constraint or stretch will either pern'ianently impair this relation, or possibly injure the component fibers themselves.

There has been hitherto some appreciation of the ill effects of excesive stretch of the drying web of paper, but, so far asvwe know, it has always been assumed that any such injury would grow progressively and proportionately from the beginning of drying, as indicated by the dot-and-dash line in Figure l. We believe that there has been no previous suggestion of the true condition disclosed by our experiments, namely, the existence of a critical moisture value above which constraint did practical-l ly no harm and below which it seriously impaired strength.

lf this increasing susceptibility to injury by mechanical constraint actually did proceed regularly and corresponded in approximate quantitative proportion to the amount of water that had been removed, then increased value of the product due to the gain in strength to be expected from any innovation in drying method that began tardily enough to be compatible with flatness, would not repay for necessary machinery and attendance; so that the mere qualitative, as distinguished from quantitative, theory of this subject would not encourage action along these lines, and in fact has not encouraged it. Ourl experiments have disclosed the previously described wide departure from direct proportionality between drying and susceptibility to injury, and the existence of the well marked critical point and range that place the commercial possibilities upon quite another footing.

As already stated, the point from which 'our experiments show that the paper must be allowed to dry with free shrinkage. it full strength is to be conserved. coincides substantially with the point at which it .first becomes dry enough to be immune from serious cockling under further drying without mechanical flattening. This result would be expected if our theory is correct, since we believe that this point marks` the removal of the last of the mechanically-held water, and the establishment of a fairly firm bond between the bers vsuch as would strongly oppose exactly that permanent change of fiber relation under locally uneven drying which is believed to subsequently' produce cockling when the paper is fully dried.

lVhether cur explanation of the facts be corre-st or not, we have definitely established the facts themselves to wit,-that the loss of strength from mechanical constraint in drying nearly .all occurs within a lather short and very definite critical moisture range; that enforced tlatneis and tension within the values usually employed do not apprecably detract from strength before this critical moisture range is reached in the process of drying; and that the beginningl of this critical range is about coincident with the moisture content at which the paper may begin substantially unconstrained drying without serious departure from ultimate flatness.

As a means of further elucidating this matter, Figure l shows a mean graphical record of a number of experiments. On this plot ordinates show strength developed by the specimen which had been dried on the machine to, but not beyond, the percentage moisture content indicated by the corresponding abscissa, and had been airdried from that point on to dryness. In other words, the moisture content at which the drying was changed from const rained to free, is plotted against the strength finally attained by the specimen, this strength being expressed as a percentage of the maxinuun strength the specilnen would have attained had it been dried without constraint from its point of delivery from the press rolls.

kFrom this curve, which directly represents results on writing papers, it will be seen that the critical point at which injury from constrained drying begins is relatively sharply defined, and that the range of moisture content, during with such drying is detrimental, is '.n the general order of a fourth of the total range. So far as is known to us, the existence of any such critical point or critical range had not heretofore been suspected by persons skilled in the practice of the art of drying paper, and even after its existence is known, there is nothing in the behavior of the paper during or after passage through the machine from which a, skilled man Would be able to deduce or infer its existence, and still less, its location; for this reason it will be necessary for persons practicing this invention to ascertain by performance of, or reference to,

' actual experiments, the critical moisture percentage and moisture range for the particular kind of paper that it is proposed to dry, and not to depend upon mere skill in the paper drying art in determining the range, through which the drying paper should be freed from strong mechanical constraint. 1t will be understood that the quantitative results would be quite different in widely dit'- ferent papers, such as papers made from a slow stock as contracted with those made from a free stock. y

ly way of a specific illustration we herewith give the mean numerical results from live series of experiments showing injury from drying various weights of a certain fairly high grade writing paper by the customary method; the paper came from the press-rolls to the ordinary paper machine drier with moisture content equal to a little over 200% of the weight of the dry fiber. The drying operation did not measurably injure the strength up to the point where the contained moisture has been reduced from this initial value ot' 200% down to (31% ot' the dry weight of the paper; the further reduction of the moisture content from Glf; to 5% of the dry weight resulted in a reduction of Mullen strength by 24.0% ot' the maximum strength possible. or otherwise stated by 31.024 of the final strength actually realized and the further `reduction ot' the moisture from 5% topractical dryness did not further injure the strength apprcciably. rlho same data are otherwise presented in Figure l. Expressing approximately the same results in terms of the moisture content of the paper as it reaches the drier, it may be said that the drying under severe mechanical const Iaint should cease when the moisture content of the paper has been reduced to 525% to 5023i; of total weight of the lnoist paper. ln other words. for all practical purposes, the critical point, at which the further drying of such paper should be without considerable mechanical constraint, lies within a range of 2591 to 50% of the moisture content depending to some extent on the stock undergoing treatment, and usually lies within .a range of 35% to 45%.

F rom this discovery it has been possible to work out important improvements in drying and the process and apparatus that we have found most advantageous will next be described with reference to the drawings. The operating details of the process, and the proportions of the apparatus will require suitable changes to meet variation in kind of paper dried; such of these changes as are not directly indicated can be readily worked out by persons skilled in the art and` conversant with this disclosure. The arrangement hcre described is one directly adapted to writing papers.

ln our process the paper in a continuous traveling web is taken Vfrom the wet end of thi Fourdrinier or other web-forming machine end dried to the first critical point previously defined, under such mechanical constraint. as.will forcibly determine flatness; it is then passed to an apparatus in which the drying is continued with the paper, free or sulliciently so to take up its own form and dimensions, and the drying is here continued at least through that phase susceptible to injury by strong stre-tch or mechanical restraint. The drying may be carried on to completion with the paper still unconstrained, but We should not regard it as a departure-from ou'r process if the paper y were transferred back to apparatus Where flatness is enforced, as soon as the phase susceptible to injury by constraint is passed.

Rference may be had to the drawings, which show an apparatus Well adapted'to carry out. this process:

Figure 1 represents the chart previously referred to; F igures2 and 2a show a side elevation of the apparatus, and Figure 3 a plan of the part in which the second or unconstrained phase of the drying is carried on. I For the first phase of drying, We prefer to use the ordinary dry part of the usual paper machine, as illustrated in Figure 2; but modifications of, or departures from, this structure, suoli as the so-called Yankee drier, or a drier Where some slatted rolls are substituted for part of the solid ones, are permissible if they still provide l for adequately holding the paper flat diiring this phase of the drying.

The second phase of the drying may be satisfactorily carried out in the Well known festoon drier, such as that illustrated or by any other drier which effects drying of the paper Without severe constraint. There are certain important operating details that should be kept in mind in the proportioning and handling of this form of drier for this purpose, and these are indicated later. Any

.equivalent form of' drier may be substituted for the festoon drier in this second phase? equivalence for this purpose meaning simil' lar ability to remove moisture evenly from v the 'paper while it passes through the drier in a condition comparatively free from mechanical stress or constraint.

The third comparatively brief phase of drying, after the paper has become so dry 1 as to have recovered immunity from injury through ordinary degrees of mechanical constraint, can, if desired, be carried out on drying cylinders similar to those of an ordinary paper machine, since the action of the felts, and the tension, promote iiatness and finish desired by the trade for most papers.

On the drawing, we have indicated at A the delivery end of a Fourdrinier machine, for which any other web-forming machine may be substituted, by which the initially wet web of paper is newly formed and at B we have vindicated a plurality of the usual press rolls Which may be of standard form. At G we have shown a standard drier einploying drier felts, to which the web is delivered from the F ourdrinier machine and the press rolls, and by which the web is nderftension and constraint, as usual to predetermined form and dimensions, during its initial drying, in accordance With our process. This drier is shown as having but the first twelve heated rolls, (out of the usual twenty-three or more) the temperature of which is controlled as ordinarily.L The number of heated rolls will naturally vary with their speed and the temperature and With the character of the paper being dried. At D we have shown conventionally an apparatus in which the drying of the paper may be continued, after it has reached the critical point of moisture content, vbeyond which severe mechanical constraint would tend to injure the ultimate product. This apparatus is used during the second phase of the drying and as shown it may include a closed casing in which the paper is festooned by any suitable festooning mechanism. This particular apparatus per se forms no essenfestooning mechanism. A damper is indi-- cated at 8, by which a portion of the moisture-laden air may be drawn from the drying enclosure at the bottom of the apparatus, and be redelivered to the heater ,6. 11 represents a fan which is employed for ensuring the circulation of the air. At the forward or receiving portion of the apparatus, there is a second top manifold 12 to which the air withdrawn through a conduit 13 leading from the manifold 9 may be supplied by a conduit 14 and a fan 15. In the conduit 14 there is arranged a heater 16 into which additional outside air may be supplied by a damper 19 and air from the apparatus may be supplied through a damper controlled conduit 23. From a manifold 2O at the-bottom of the first portion of the apparatus, the air is withdrawn by a fan 21 and discharged through a conduit 22. The drying of the paper may be completed in this apparatus, although for some purposes it may be desir: able to again subject the paper to drying `under restraint, and consequently we have shown at E several rolls of the usual standard drier equipped with the drying felts, As We have alreadystated, it is not at all necessary in the second phase of drying to lemploy a festooning apparatus, as We may ing this second phase of the drying may be freed from constraint without danger of cockling.

lith regard to the proportions and adjustments of the apparatus, the following maybe said:

The earlier part of the drying, which is carried out on ordinary paper-machine dryers, will present only one unusual diiiiculty to persons skilled respectively in the arts. of paper-machine designing and papermachine opera-tion; namely, the substitution of theA requirement that the percentage of moisture in the paper at the end of this section be held within relatively narrow definite limits, for the less severe customary requirement that the paper emerge with any moisture content lessthan a specified small amount. It is well known that the discharge 'of moisture from the wet paper as it passes over the successive drying drums or cylinders of the paper-machine drier is at first rather slow; that after the paper and its contained water is heated to nearly the boiling point by contact with the earlier hot drums this rate of discharge becomes materially greater; and that when drying 1s nearly complete it becomes much less again because there is little moisture left -to evaporate; so it will be understood that the fact that this lirst section removes say, 70%

` of the amount of moisture that the paper initially contained does not imply that just as many drums should be used as in a complete drier of usual form. As an example of this, experiments with certain writing papers showed in that particular case the best results were obtained with a first section having the first l2 rolls, of a iZ3-roll machine. The proportions of this first-phase drier having once been fixed, working adjustment can be obtained by variation of steam pressure and consequent temperature of the drying steam in the drums, by variation in the speed of the drums and in some measure, by control of the pressure of the press-rolls. It will be understood that to secure the best results the operation must be controlled carefully, since an exact end point is sought at a phase of the drying where the discharge of moisture is rapid; while in ordinary practice an approximate eind point` is permissible, and the iin-al phase is one where the moisture discharge is slow.

In the second part of the drying where the paper is free from any strong mechanical constraint, a suitable (but not the only) method of carrying ott' the contained moisture is by means of a current of air, as in the festoon drier illustrated. In using such a method it is desirable that the location of delivery, the temperature, volume, and humidity of the air -serving this function be so regulated that the edges will not dry betore the middle of the Web, 11er the outside of the lsheet too much faster than the inside. It is of course also highly desirable that the rate of drying should be as high as may beA compatible with these conditions. The end point for the unconstrained drying need not lustrated in Figure 2, and its design and I its operation will present no unusual ditiiculties to those skilled in these respective arts. Of course if the paper is thereafter subject to some after-process that wets it, as top sizing, it must be dried again, but our process is directly concerned with only the initial drying.

`Paper dried in a continuous web in a machine of the character just disclosed diflers from that dried in the usual way, wholly under constraint, principally in the possession of materially higher strength; there are also certain other differences 1n the matter `of texture, feel and finish, all of which, so far as we are aware, further contribute to conferring upon the product a higher degree of utility and value vthan it would have possessed had the drying process and apparatus been of standard character.

This sequence of drying opera-tions as herein disclosed, must start with the newlyformedwet sheet, and be carried on continuously, in order to produce the most valuable results; that is, the papermust not have been dried before and afterward wetted again; and itA should not be partially dried under constraint, rolled up, and subsequently or elsewhere transferred for further drying to an apparatus exerting no strong constraint. The reason for the first limitation is that if the natural bond between the fibers is once 4weakened by detrimental drying methods such as universally heretofore practiced, the injury cannot be repaired by any after-treatnient. The reason for the second limitation is 'that paper, so wet as is that at the point of transfer, cannot by any known feasible process or, system be rolled up, stored, transported and re-handled without such serious injury and loss as would more than offset the benefits of the process.

Paper dried in accorda-nce with our process may .undergo immediate or deferred after-treatment suoli as tub-sizing, and it will maintain the increased strength and improvement in texture Without impairment by such after-treatment, and in the case of tub-sizing, will derive v as much additional benefit in the matter of added strength from j the topsize as it would have done had it ,our process is one for conserving the natural maximum strength of the paper and preventing injury or detriment thereto during the process of drying; and is not a process for conferring additional strength by any after-treatment to be administered to a web or sheet that has already been once dried,

or of so administering any such after-treatment as to maximize the additional strength so conferred. Ourv product is susceptible equally with the product of methods heretofore used, of modification by, or benefit from such after-treatments, however administered. Its very substantial inherent advantages over the product ofdrying methods heretofore standard, is due to the removal by our process of a seurce of injury which has hitherto been present-not to the addition or manipulation' of any agent or treatment adapted to confer desirable qualities after the paper has once been injured during its first drying.

I-Iaving thus explained the nature of our invention and the principles of the necessary loperation of instrumentalities employed in connection with the process, but without attempting to set forth all of the various in- ,strumentalities which might conveniently be used since we make no claim to any instrumentality per se, what we claim is:

l. The herein described method of drying paper, which consists in progressively re# moving from the initially wet newly formed paper, as it is delivered from the web-forming machine and while under mechanical restraint, a portion of its contained moisture to a point at which flatness of the ultimate product is secured and beyond which injury to the strength of the ultimate productwould result, and then drying the paper while substantially free from severe mechanical constraint.

2. A process of drying paper, which consists first in progressively drying an initially wet new-ly formed ltraveling web of paper,

while mechanically constra-incdvto substan tially 'determinate form until the moisture content is reduced to a point beyond which further constraint would cause 'in-jury to the strength of the ultimate product, and, second, in further progressively drying such paper without substantial mechanical constraint. f

3. The following process for drying paper, to wit: first, subjecting an initially wet newly formed traveling web of paper to progressive drying, while being forcibly held to substantially determinate form and dimenously subjecting the same to further progressive drying without any considerable degree of such constraint, until the moisture content has been further reduced to a second value at which immunity from injury by customary degrees of mechanical restraint is reestablished; and, third, completely drying the web while under constraint.

4. A. process of drying paper which consists in drying the newly formed web of paper down to a certain critical moisture content under such relatively strong mechanical constraint as will forcibly determine fiatness, and immediately thereafter further drying it at least down to a second critical moisture content, without any considerable constraint; the two critical moisture values being defined as boundaries of a critical moisture region throughout which the progressively drying web of wet or damp paper suffers important injury to strength from any strong constraint, an( outside of which it suffers no such injury therefrom. I

5. A- process of drying paper which com sists in causing a traveling newly formed initially Wet web of paper to be passed under tension through the heated rolls of a suitable drier until a point is reached beyond which injury to the strength of the ultimate productwould result, and then removing tension from the web and further drying the same until the desired point of moisture content is reached.

6. The herein described process of drying writ-ing paper, which consists in first subjecting a traveling newly-formed web of initially wet paper to progressive drying, while being mechanically constrainedto substantially definite form, until the moisture content is reduced to a point lying between 25% to 45% of the total weight, and then progressively further drying such partially dry web free from any considerable degree of mechanical constraint.

In testimony whereof we have afiixed our signatures.

EMIL A. BRINER. HENRY J. GUILD. 

